As is well known, because the basic material of optical disks is synthetic resin, they may deform in a curve when formed. When a deformed disk is loaded onto a turntable of an optical disk drive, the recording surface of the optical disk is tilted with respect to an optical pickup, and laser light that is emitted from the optical pickup may not be radiated perpendicularly onto the recording surface of the optical disk. In this state, the spot of the laser light on the recording surface of the optical disk deforms generating coma aberration, and causing recording and reproduction errors of the optical disk.
Thus, for example JP H9-7207A discloses a technique for detecting the tilt angle (amount of tilt) of a recording surface of an optical disk while adjusting the tilt of a laser light axis from an optical pickup in accordance with the amount of tilt that is detected, and causing the laser light that is emitted from the optical pickup to be perpendicularly incident on the recording surface of the optical disk to correct the amount of tilt.
FIG. 3 shows an example of a conventional optical disk drive device. In this device, an optical disk 101 is clamped between a damper 102 and a turntable 103, and the turntable 103 is rotated by a spindle motor 104. Furthermore, the spindle motor 104 is fixably supported by a main chassis 105. One end of a sub-chassis 106 is linked to the main chassis 105 by a shaft 106a to support the sub-chassis 106 such that it is capable of tilting, and the other end of the sub-chassis 106 is freely supported by a support member 110 such that the sub-chassis 106 can move vertically with respect to the main chassis 105, and the other end of the sub-chassis 106 is elevated by a height adjusting mechanism 107 to control the tilt of the sub-chassis 106. A guide shaft 108 is fixed above the sub-chassis 106, an optical pickup 109 is supported by the guide shaft 108 such that it can freely move in the radial direction of the optical disk 101, and the optical pickup 109 is moved by a carrying mechanism 111. A tilt sensor 112 for detecting the tilt of the optical disk 101 is provided on the optical pickup 109.
Thus, while moving the optical pickup 109 in the radial direction of the optical disk 101, the amount of tilt of the optical disk 101 is detected by the tilt sensor 112 at the same time as recording or reproducing the optical disk 101 with the optical pickup 109, the tilt of the sub-chassis 106 is adjusted in accordance with the amount of tilt of the optical disk 101 by the height adjustment mechanism 107 to adjust the tilt of the optical pickup 109, and the laser light that is emitted from the optical pickup 109 is perpendicularly irradiated onto the recording surface of the optical disk 101. Thus, the amount of tilt is corrected.
Furthermore, JP 2000-76679A discloses a technique in which an optical pickup that contains two optical system for handling two different types of optical disks is used, wherein when one optical system is used for recording or reproducing an optical disk, the amount of tilt of the optical disk is detected by the other optical system.
However, in the techniques of both JP H9-7207A and JP 2000-76679A, the position for detecting the amount of tilt of the optical disk is fixed with respect to the position for recording or reproducing the optical disk, and it has not been possible to adjust (move) the position for detecting the amount of tilt with respect to the position for recording or reproduction during recording or reproduction. For example, in the technique of JP 9-7207A, it has not been possible to let the position for detecting the amount of tilt coincide with the position for recording or reproduction.
Furthermore, in the technique of JP 2000-76679A, if the laser wavelengths differ, then when one optical system is focused for recording or reproducing an optical disk, the focus of the other optical system is lost. Thus, the detection of the tilt of the optical disk with the other optical system may be adversely affected by fluctuations in, for example, the thickness of the substrate or refractive index of the optical disk.
Thus, in view of the above-noted conventional problems, and on the precondition that at least two optical pickups are provided for recording or reproducing optical disks such as CD (Compact Disc) and DVD (Digital Versatile Disk), it is an object of the present invention to provide an optical disk drive device that is capable of adjusting the position for detecting the amount of tilt in the radial direction of the optical disk with respect to the position for recording or reproduction while detecting the amount of tilt at the same time as recording or reproducing the optical disk, and to provide a method for correcting the tilt of the optical pickup.